1. Field of the Invention
The present invention relates to a sheet cutting apparatus for cutting a sheet bundle to be cut by a cutting device, a sheet processing apparatus, and an image forming apparatus, in particular, a construction for achieving an improvement in productivity.
2. Description of the Related Art
Some conventional image forming apparatuses for forming images on sheets, such as a copying machine, a printer, a facsimile apparatus, and a multi-function apparatus composed of a combination of these apparatuses, are equipped with a sheet processing apparatus for processing a sheet on which an image has been formed by an image forming portion. Some of such sheet processing apparatuses are equipped with a sheet cutting apparatus for cutting a sheet, a sheet bundle, etc. (hereinafter referred to as a sheet bundle to be cut) by a cutting knife, which is an example of a cutting means.
In such a sheet processing apparatus, sheets discharged from the main body of an image forming apparatus are bundled to be subjected to paste bookbinding or saddle stitching folio bookbinding, and the end portions of the sheet bundle are cut by the above-mentioned sheet cutting apparatus so as to align the book end surfaces (see, for example, JP 2003-292230 A). Not only a sheet bundle but also a single sheet may be cut by the sheet cutting apparatus.
In order to cut a sheet bundle to be cut by such a conventional sheet cutting apparatus, the sheet bundle to be cut is first secured in position by a sheet presser means, and then the sheet bundle to be cut is cut by the cutting device. When the sheet bundle to be cut is thus pressed, the sheet presser device starts the operation from the same standby position regardless of the number of sheets of the sheet bundle to be cut or the thickness thereof.
In order to cut a sheet bundle to be cut by such a conventional sheet cutting apparatus, the sheet bundle to be cut is first secured in position by a sheet presser means, and then the sheet bundle to be cut is cut by the cutting device. When the sheet bundle to be cut is thus pressed, the sheet presser device starts the operation from the same standby position regardless of the number of sheets of the sheet bundle to be cut or the thickness thereof.